If one estimates the colonies strength by multiplying the number of frames of bees by 1500 per deep frame or 1000 bees per medium frame one can estimate the number of bees in the colony, and if this number is divided by the mite fall after a treatment and then multiplied by 100 we will get a figure of the number of phoretic mites per 100 bees and also have the advantage of doing away with a lot of mites but could be used instead of an alcohol wash.  To try to apply a continuous stream of oxalic vapor in a small enough amount as not to interrupt the colonies normal activities and still be able to spread the tiny crystals might be a lot to ask for. I wonder what the effect of glycerin soaked towels laid on top bars and even on the floor might have on extending the effective time of oxalic vapor as many crystals would end up on the towels and could be replenished with the next treatment to some extent.  There is also little chance of the vapor condensing with a band heater type of vaporizer unless the nozzle is discharging directly onto a frame close by as the hot vapor solidifies into tiny crystals similar to fumed silica within 2 to 3 inches of leaving the nozzle and tend to fall soon after,  the reason I advocate treating from above the brood area.
John from the Northern Neck of Virginia. 

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